全文获取类型
收费全文 | 1628篇 |
免费 | 119篇 |
国内免费 | 1篇 |
专业分类
林业 | 59篇 |
农学 | 23篇 |
基础科学 | 19篇 |
194篇 | |
综合类 | 335篇 |
农作物 | 42篇 |
水产渔业 | 43篇 |
畜牧兽医 | 918篇 |
园艺 | 32篇 |
植物保护 | 83篇 |
出版年
2021年 | 12篇 |
2020年 | 31篇 |
2019年 | 20篇 |
2018年 | 29篇 |
2017年 | 28篇 |
2016年 | 41篇 |
2015年 | 23篇 |
2014年 | 25篇 |
2013年 | 54篇 |
2012年 | 56篇 |
2011年 | 72篇 |
2010年 | 42篇 |
2009年 | 35篇 |
2008年 | 67篇 |
2007年 | 64篇 |
2006年 | 49篇 |
2005年 | 48篇 |
2004年 | 52篇 |
2003年 | 52篇 |
2002年 | 45篇 |
2001年 | 51篇 |
2000年 | 43篇 |
1999年 | 32篇 |
1998年 | 29篇 |
1997年 | 31篇 |
1996年 | 25篇 |
1995年 | 12篇 |
1994年 | 12篇 |
1993年 | 18篇 |
1992年 | 26篇 |
1991年 | 24篇 |
1990年 | 27篇 |
1989年 | 46篇 |
1988年 | 37篇 |
1987年 | 36篇 |
1986年 | 37篇 |
1985年 | 19篇 |
1984年 | 18篇 |
1983年 | 22篇 |
1982年 | 15篇 |
1979年 | 19篇 |
1978年 | 16篇 |
1977年 | 15篇 |
1976年 | 17篇 |
1974年 | 17篇 |
1973年 | 19篇 |
1972年 | 23篇 |
1970年 | 18篇 |
1969年 | 12篇 |
1968年 | 12篇 |
排序方式: 共有1748条查询结果,搜索用时 0 毫秒
991.
A 14-month-old entire male Old English sheepdog was presented with a slowly enlarging subcutaneous soft tissue swelling caudal to the last rib. Radiographic and ultrasonographic Investigations demonstrated a soft tissue mass closely adherent to the body wall, with a coarse hypoechoic pattern. Surgical exploration revealed a mass with the gross appearance of splenic tissue. The mass was adhered to a healed paracostal abdominal tear. Histological examination confirmed the resected tissue to be normal spleen. 相似文献
992.
Hopper SA Schneider RK Johnson CH Ratzlaff MH White KK 《American journal of veterinary research》2000,61(12):1633-1635
OBJECTIVE: To compare transfixation and standard full-limb casts for prevention of in vitro displacement of a mid-diaphyseal third metacarpal osteotomy site in horses. SAMPLE POPULATION: 6 forelimbs from 6 horses euthanatized for reasons not related to the musculoskeletal system. PROCEDURE: A 30 degrees osteotomy was performed in the mid-diaphysis of the third metacarpal bone. Two 4.5-mm cortical bone screws were placed across the osteotomy site to maintain alignment during casting. Two 6.35-mm Steinmann pins were placed from a lateral-to-medial direction in the distal aspect of the radius. A full-limb cast that incorporated the pins was applied. An extensometer was positioned in the osteotomy site through a window placed in the dorsal aspect of the cast, and after removal of the screws, displacement was recorded while the limb was axially loaded to 5,340 N (1,200 lb). Pins were removed, and the standard full-limb cast was tested in a similar fashion. RESULTS: The transfixation cast significantly reduced displacement across the osteotomy site at 445 N (100 lb), 1,112 N (250 lb), 2,224 N (500 lb), and 4,448 N (1,000 lb), compared with the standard cast. CONCLUSION AND CLINICAL RELEVANCE: A full-limb transfixation cast provides significantly greater resistance than a standard full-limb cast against axial collapse of a mid-diaphyseal third metacarpal osteotomy site when the bone is placed under axial compression. Placement of full-limb transfixation casts should be considered for the management of unstable fractures of the third metacarpal bone in horses. 相似文献
993.
ABSTRACT The inheritance of resistance to Aspergillus ear rot and aflatoxin production in corn (Zea mays L.) caused by Aspergillus flavus was studied in progeny derived from crosses between the resistant corn inbred cv. Tex6 and susceptible inbred cvs. B73 and Mo17. From 1994 to 1996, plant generations included were the P(1) (susceptible B73 or Mo17), P(2) (resistant Tex6), F(1), F(2), F(3), BCP(1), BCP(1)-selfed, and BCP(2). The BCP(2)-selfed generation was added in 1995 and 1996 for the B73 x Tex6 cross. Primary ears were pinboard inoculated and evaluated for Aspergillus ear rot severity. F(1) means deviated from the midparent value toward resistance for aflatoxin production and toward susceptibility for ear rot in both crosses. Analyses of generation means indicate that additive gene action was most important in the resistance to both ear rot and aflatoxin production in the B73 x Tex6 cross. Mo17 was somewhat resistant to both traits, so resistance from Tex6 was not well defined in this cross. Broad-sense heritabilities for ear rot and aflatoxin production were 58 and 63% for Mo17 x Tex6, and 66 and 65% for B73 x Tex6. Narrow-sense heritabilities for ear rot and aflatoxin production were 39 and 45% for B73 x Tex6. It is estimated that one cycle of selection for resistance within B73 x Tex6 F(3) families would reduce the percentage of ear rot severity by 8.5% and aflatoxin concentration by 19 ng/g. 相似文献
994.
Ronan A. Mullins Antía Escribano Carrera Davina M. Anderson Jean-Philippe Billet Herve Brissot Cameron Broome Hilde de Rooster Barbara M. Kirby Kathryn M. Pratschke Michael S. Tivers Robert N. White Donald A. Yool K. Ruth Youmans 《Veterinary surgery : VS》2022,51(1):23-33
The development of postattenuation neurologic signs (PANS) is a poorly understood and potentially devastating complication after surgical attenuation of congenital portosystemic shunts in dogs. Postattenuation neurologic signs include seizures but also more subtle neurologic signs such as depression, behavioral changes, tremors, and twitching. They most commonly occur within 7 days postoperatively and are typically unrelated to hyperammonemia, hypoglycemia, or electrolyte disturbances. This narrative review summarizes the findings of 50 publications from 1988-2020 that report occurrence of PANS. While most published reports included only dogs affected by postattenuation seizures (PAS), others included dogs with any form of PANS. Overall, PANS (including PAS) affected 1.6%-27.3% of dogs, whereas incidence of PAS ranged from 0%-18.2%. The etiology of PANS remains unknown; however, several theories have been proposed. Risk factors include preoperative hepatic encephalopathy, increasing age, and possibly certain breeds and extrahepatic shunt morphology. There is increasing evidence that prophylactic antiepileptic drugs do not prevent PANS. Treatment is centered around controlling neurologic signs with antiepileptic drugs and providing supportive intensive care. The 30-day survival rate in studies that included a minimum of four dogs affected by PANS was 0%-100% (median, 50.0%) and 0%-75.0% (median, 37.5%) for those with PAS. Mortality associated with PANS was typically related to occurrence of generalized seizure activity. Prognostic factors positively associated with short-term survival included having a history of preoperative seizures and development of focal seizures only. If affected dogs survived to discharge, survival for several years was possible, and the majority of neurologic signs manifested as part of the phenomenon of PANS appeared to resolve. 相似文献
995.
Bud dormancy of root wrenched and unwrenched slash pine (Pinus elliottii Engelm.) seedlings growing in a forest nursery was measured on five lifting dates. Determination of bud dormancy was based on days to budbreak (DBB) under optimal growing conditions, mitotic activity in the apical meristem, chilling hours accumulated, and bud morphology. Based on DBB, seedlings were most dormant at Lift 2 on November 24 after exposure to 189 hours below 10 degrees C and 93 hours below 6.7 degrees C. Mitotic activity in the apical meristem was at its lowest 23 days later at Lift 3, possibly indicating the period when seedlings are most resistant to transplanting stresses. Multiple wrenching resulted in a slight shift in the dormancy cycle as wrenched seedlings set bud sooner in the nursery and broke bud sooner at the planting site in the spring than control seedlings. This implies that wrenched seedlings can be successfully lifted from the nursery earlier and will initiate spring shoot growth earlier than control seedlings. 相似文献
996.
The White House 《Journal of pest science》1964,37(1):16
Ohne Zusammenfassung 相似文献
997.
Timothy L. White 《New Forests》1987,1(4):325-342
Forest tree improvement programs have become quite complex and program strategies and intensities vary dramatically around the world. It is often necessary to examine the reasons for each activity separately in order to ascertain how all steps fit together in a strategy aimed at achieving genetic gain. This paper establishes a conceptual framework that explains the purposes of the various activities of tree improvement and allows complicated program strategies to be easily conveyed. This conceptual model, called the breeding cycle, stresses why, not how, each activity is conducted. The breeding cycle turns around one time for each generation of breeding and is composed of various types of plant populations. Each plant population serves a role in the tree improvement program and is created form a preceding population in the cycle by an activity of the breeder.Tree improvement concepts are explained and the roles of genetic test plantations are described in the context of the breeding cycle. This conceptual model is useful for foresters responsible for implementing tree improvement programs, for students and breeders trying to understand and compare divergent program strategies and for managers responsible for making investment decisions. 相似文献
998.
999.
White SD Affolter VK Schultheiss PC Ball BA Wessel MT Kass P Molinaro AM Bannasch DL Ihrke PJ 《Veterinary dermatology》2007,18(1):36-40
A Quarter horse filly bred from two horses affected with HERDA (hereditary equine regional dermal asthenia) was observed clinically and its skin histologically for the 1.5 years of its life. Severe signs of the disease did not manifest until 1.5 years of age, and were not temporally related to saddling. Histological comparison to an age-, breed- and sex-matched control did not show any consistent diagnostic features. Monitoring of the proband substantiated previous reports of (i) the autosomal recessive nature of the disease, (ii) mares affected with HERDA being able to foal without damage to the skin or reproductive tract, (iii) HERDA foals appearing phenotypically normal throughout the first year of life, and (iv) demonstrated that histological interpretation of skin specimens from grossly normal skin may be insufficient to differentiate HERDA-affected horses from controls. 相似文献
1000.
Outcome of palmar/plantar digital neurectomy in horses with foot pain evaluated with magnetic resonance imaging: 50 cases (2005–2011) 下载免费PDF全文